


Believer

by Lici_Rose



Category: Underfell AU - Fandom, Undertale (Video Game)
Genre: Alternate Universe - Soulmates, Alternate Universe - Underfell, F/M, Fluff and Smut, One Night Stands, Reader and Sans are into kinky shit, Self-Insert, Shameless Smut, Soulmate AU, Underfell Papyrus, Underfell Sans, You Are an Art Student BTW, sorry i suck at tags
Language: English
Status: Completed
Published: 2017-11-18
Updated: 2018-06-21
Packaged: 2019-02-03 20:51:32
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 4,329
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12755988
Author URL: https://archiveofourown.org/users/Lici_Rose/pseuds/Lici_Rose
Summary: I was really inspired by a dream I had about Sans from Underfell, which will only be a few chapters long, but hopefully you all enjoy! <3





	1. Karaoke Night

**Author's Note:**

> This will be my pilot chapter, so I'll continue it based on the feedback :) Let me know if you want more! Even just a kudos will help <3

Awareness creeped up on your consciousness far slower than usual as you woke up. You could already feel your hangover pounding in your head, but this was nothing new. You kept your eyes closed. All you had to do was walk over to the bathroom for some pain-killers, take a hot shower, and you’d be fine. You’d nursed enough hangovers to handle it. You curled up in your covers, chuckling as you found that you had slept naked again. But as you felt an arm snake it’s way around you, you froze. Your eyes shot open, the room still dark. You looked at the alarm clock on the lamp table next to the bed, which revealed that it was 5:37 in the morning, about the time you usually wake up for class, your body had woke you up at the usual time without an alarm clock, and you usually would have been impressed, but there was a more pressing matter at hand. Where the hell were you? Who the hell was sleeping beside you? You laid there, trying to remember the night before, yet you could only remember bits and pieces. You figured that it was now Saturday morning, and that you didn’t have to work, thank God. You remember getting shit-faced as usual, and flirting with someone… God, this annoyed you. You could barely remember the bar you were even at. Shit. 

You hoped and prayed that whoever was sleeping next to you was a heavy sleeper, because you planned on booking it as soon as you had your clothes back on. You reached up to pull the arm away, and nearly squealed as you felt… A bone arm?! Ah, now you could remember the golden glint of a skeleton tooth as you made him smile and laugh. Yet, you couldn’t think of a face or name. Even though the arm had startled you, you didn’t cringe as you set the arm behind you, carefully wiggling off the bed. The bed had creaked several times as you had gotten out of it, yet he didn’t even stir. You could hear his soft snoring, so at least he wasn’t unconscious. The room was dark, the blackout curtains shielding you from the early light of morning. You shuffled around, finally finding your phone in the pocket of your jeans. Surprisingly, it was at half battery, so you used your flashlight to find your clothing. Thankfully, your panties were inside of your jeans, since the flimsy fabric would have been hard to find. You slipped them on, and found your shirt next, a maroon sleeveless turtleneck. But now the only thing that was missing was your bra. You searched the room as silently as you could, but the hardwood floor constantly creaked, and you felt fear creep up on you, and your splitting headache begged you to get back into bed. You didn’t want to wake him up, trying to avoid an awkward conversation at all costs, since you couldn’t even remember his name. Giving up on that endeavor, you slipped on your turtleneck and jacket, deciding to leave without it. You debated leaving your number on the nightstand, but you decided against it, so you carefully opened the door, slipping out of the bedroom. The light from the outside room revealed his features, where you found that he was almost… Handsome? He looked so peaceful, you almost felt bad about slipping out like this, but you had to leave. 

You carefully closed the door behind you, sighing as you heard the soft click of the door. You looked around, noticing that you were now on a loft, and you could look down into a living room and a kitchen, where new appliances and modern furniture showed this monster’s wealth. You groaned, massaging your head as you walked down the stairs. You froze, squeaking instead of screaming as you heard someone clear their throat behind you. You turned, craning your head up to see a taller, thinner skeleton at the top of the stairs, clad in silk pajamas and robe. There even was a cursive “P” embroidered on the robe. You awkwardly waved, gulping. He kind of looked like the skeleton that was in the bedroom, so you figured that they were related in some way. You took note of the large crack on his right eye socket, stretching wide, giving him an even more intimidating demeanor. 

“Uh, hi. I’ll be honest, I don’t know where I am. I… Must have drank too much last night.”

The tall skeleton huffed, walking down the stairs. “PITIFUL. THE OTHER WOMEN THAT COME HERE AREN’T USUALLY THAT STUPID.” He sighed, “THERE’S A BUS STOP JUST AROUND THE CORNER IF YOU GO SOUTH ON THIS STREET, HUMAN.”

Okay, now he’s using the compass to give directions. Fuck. “Uh, thanks. My head hurts too much to care about you calling me ‘human,’ so, bye.” 

The skeleton scoffed, turning on the coffee machine. Seems talking won’t do much else. So you opened the door, slipping out of the house, trying to piece together your night. You were curious what events lead you to go home with a skeleton monster. You were only curious what might have taken place last night, since skeleton anatomy was something you had no clue about. Yet you felt sore enough to know that something had happened last night that you wished you could remember.

The farther you walked away from the house, the more a tightness in your chest grew. Stressed about finals coming up, you blamed it on general dread for the upcoming week as you shrugged off the feeling. Looking around, you immediately recognized the neighborhood you were in. Close to the student ghetto of your college, where you and a few friends were renting a house, there was the monster neighborhood, were a good amount of the population lived. Most people were too scared to live too close to the violence-hungry monsters, but you learned that the violence-hungry was a myth, the monsters becoming more kind, yet cautious, when they were finally free. One of your friends had interviewed several monsters for the student newspaper, which is how you learned of the conditions of the Underground. You couldn’t blame them for being cautious on the surface. It would take a lot of time to settle down and learn to trust humans, at least the humans who were decent.

 

. . .

 

“Oh, my god, Y/N. You went home with a Skeleton?! What did it feel like? Was he huge? You had better spill the beans right now!” Your friend, Katherine screeched when you finally came home around 6:30, since she and her girlfriend were both morning people, you weren’t surprised to see Katherine’s smug face as you took the walk of shame. 

“Kat, I need drugs and a shower before I can answer any of that.” You set down your stuff, kicking off your shoes.

Her girlfriend, Jasmine, groaned on the couch, also nursing a hangover. “Sorry, girl that I flaked out on you last night, I had to leave that stupid bar after I threw up on the poor dude sitting next to me. Hopefully she can clean it off her scales…” She laid back down, face down on the couch.

“It’s fine, just scary since I don’t remember anything. Hey, Jazzy, what was the name of that bar we were at?” The only response you got was her loud snore.

“Did you at least get his number?” You loved Kat, but she could stay out of it for the moment, until you were able to shower.

“No, I don’t even know his name.” You chuckled, “And I probably won’t see him again.” You felt that tightness in your chest pulse again, so you finally escaped to the bathroom, where you were finally able to clean yourself off. But you gasped as you stripped down. You had bruises on your hips and waist. The deep purple on your already tan skin stood out, and you gingerly brushed your fingers over the marks and your stretch marks. As a thicker woman, you used to be self-conscience of those marks, but now you didn’t really care. Looks like you wouldn’t be wearing crop tops for a while. 

You slipped into some comfy shorts and a t-shirt, tying your hair into a towel and sat with your giant sketchbook, inspired to sketch out an idea you had when you were riding the bus. You looked up the reference for a skeleton, surrounding the body with flowers. You admired the work, determined to stare at it until you hated it, a common problem with artists. You had a habit of disliking your drawings because they didn’t turn out the way you imagined, yet many still enjoyed your art, even some of your professors. There were scars on the bones, and at first you weren’t sure why you added that detail. On a roll, you got out your ink pens, outlining the sketch. As a final touch, you used water colors to fill in the flowers, and a golden tooth… Holy shit, you hadn’t meant to draw him, but you had been so focused on the drawing that you hadn’t noticed the resemblance. 

You slammed your sketchbook shut, blushing wildly because for the first time in your life, drawing a naked skeleton felt extremely lewd. 

 

. . .

 

-7 Hours Ago-

Sans sat at the bar of Grillby’s, leaning on the cold countertop as he drank shot after shot of spiked mustard, a special drink of Grillby’s that was his usual. He was casually flirting with some new pretty face when he noticed that karaoke was starting, the announcement inviting anyone who wanted to join. Shit, he usually avoided this night, since he found it annoying. The girl he was talking to was a little too drunk for his taste, her slurred words becoming more and more unattractive. She was trying to casually touch him, stroking the fur of his hood, but petting a bit too hard. He preferred someone who could handle their liquor if he was going to take them home. He was horrible, but he wasn’t horrible enough for anything non consensual. But as a song he recognized began to play through the speakers, he turned around in his seat, leaning his arms on the counter behind him, surprised to see a pretty hot human standing on stage as if she belonged there, the confident glint in her eye different from the usual glint from liquid courage alone. She matched the drum beats with her movements, dancing to the intro. She seemed like the kind you didn’t want to mess with.

_First thing’s first imma say all the words inside my head_  
I’m fired up, and tired of the way that things have been  
The way that things have been.

Intrigued by the performance, Sans couldn’t seem to tear his eyes away, tapping his foot to the song. He smiled, chuckling when you started to dance on stage, meeting his gaze. You pointed at him, winking as you sang the fast parts of the song.

_But they never did, ever lived, ebbin’ and flowin’ inhibited, limited, ‘till it broke up and rained down, it rained down, like_  
Pain,  
You made me a, you made me a, believer, believer.  
Pain,  
You break me down, you build me up, believer, believer..

As he listened closer to the lyrics, he noticed more and more of himself in the song. At one point, you locked eyes with him, and he couldn’t figure out how he had stood out enough in the small crowd, since there were plenty of other more unique monsters and humans scattered around. He winked at you, amused that a blush didn’t creep across your cheeks. Seems like he’d have to try harder than that to fluster you, and he was determined to find out what would.

Encouraged by the applause, you chose another song to sing, moving your hips along to the beat of the beginning of the song. You seemed to be getting really into that particular song. 

_Black ocean, cold and dark_  
I am the hungry shark, fast and merciless  
But the only girl who could talk to him  
She couldn’t swim  
Tell me what’s worse than this?.

You leaned back as the climax of the song hit, the notes ringing out.

_I can’t fucking breathe!_  
Much less believe  
The truth  
I pick up this gun  
Aim for the sun  
And shoot!.

Okay, so he was definitely talking to this girl now. And luckily, you had waltzed right up to the bar counter, where he offered you a drink.

“Hey there, sweetcheeks, that drink’s on me. And if I play my cards right, you will be too, whaddaya say?” He winked, hoping a more direct approach would work on you.

You laughed. You actually fucking laughed. Not a polite, flirty laugh, but a genuine laugh. “Wow, no one has flirted with me like that in a while. Usually it’s creepy, but I’d like to see where this leads. I saw you watching me very intently when I was singing.” 

Sans chuckled, “I don’t beat around the bush, baby. And I gotta admit, that was quite a show. I like your taste in music, but I have yet to find out how much I like your taste in other things.” 

You both chatted for a while, flirting back and forth. You handled the alcohol well, and you tried to convince Sans to dance, something he never did. You failed, of course. So instead, he asked you if you’d walk him home. 

“Hey, that’s my line to get you in my bed! Hah, sure, let’s do this.” You winked. Seems like you were the kind to not beat around the bush either. 

He blamed it on the drinks as he felt something stir within him as you agreed. He expected an awkward silence as you both walked, but you were good company. You smiled widely as he pinned you against the wall when you finally arrived at his place, hushing you with his fiery kiss. He groaned as you eagerly invited his advances, immense pleasure flooding his senses, sparking everywhere he touched, and everywhere you touched. He found himself holding your hips too tight at times, as your desperate mews and moans filled the air around him, surrounding only the world around you both. That night was what he could only describe as the best sex of his life. There was something about the spark of your touch that left him wanting more of you. He slept better that night than he had in awhile, sleeping deep enough not to notice when you slipped away in the early hours of morning. But he remembered everything. And he was freaking out.


	2. At Last

**Notes for the Chapter:**

> Oh my gosh, I'm sorry for making you all wait so long for a part two!!! Here it is, at last!

You went about your usual week, not doing much but work on commissions and lounge about. You had lost your job a while ago, and had been eagerly searching since then. But since the school season was coming to a close, most places had already hired their summertime crew, which left you without many options. So you opened commissions, enjoying the few requests you’d gotten. A handful of requests were NSFW, which were your personal favorite. Something about the naked body was incredibly beautiful to you, and since you had taken so many anatomy classes, the naked body didn’t even fluster you in the slightest. Except when you thought of a certain scarred one, the bones glinting in the morning light…

You shook this thought away, brushing off the pinching feeling in your heart. 

You couldn’t keep that skeleton out of your head, for whatever reason. You had had your share of one-night stands, but you were able to move on easily, since you weren’t emotionally attached to any of them. Call you cruel, but you didn’t like long term relationships. The way couples would gush over each other in public just seemed gross. But, something had changed. Something in your mind was screaming that you should have left your number, that you never should have left that room. You felt sick, a pit of dread in your stomach ever since that night. Even as you tried to suppress any thought of the skeleton, it only made you think of him more. Perhaps if you pried the name of the bar from Jasmine, maybe he’d be there… 

You groaned, there you go again thinking of ways to see him again. Usually you’d avoid the person you’d slept with like the plague, not wanting any sort of attachment. There were a few guys and girls that tried to reach out to you in the past, but you never replied to their texts, hoping they’d lose interest eventually. You kept telling yourself that you hadn’t given him your number for this reason, so he wouldn’t be too clingy and annoying. But somehow, you felt in your gut that he wasn’t that type. 

You pushed your chair away from your desk and your artist tablet. You peeled off the two-fingered glove, plugging in your pen (why should a stylist need to charge??) before turning your fan on higher. Refusing to pay too much for the electricity bill, you hardly used the hunk of metal hanging in your window. You had rented an old house with your friends in a close neighborhood to the university, splitting the bills. The old victorian house was charming, and in the two years you had lived in it, it had proven to be reliable enough. You ran your fingers through your hair, sweat clinging to your face. Why were you so hot?? You huffed, stomping down the stairs to the kitchen, where Jasmine was attempting to make an omelette.

“Yo, Jaz.” You greeted her lazily, your voice hoarse.

 

Jasmine barely gave a greeting before commenting on your state, “Girl, have you been sleeping at all? You don’t look so good.” 

 

“‘S fine, I’ll sleep when I’m dead.” You had a history of pulling all nighters, but lately it had gotten worse. Drawing helped, but a bright screen didn’t. 

 

“Shit. I guess I’m eating scrambled eggs. Want some?” She had tried to flip the eggs too early, and ruined the omelette that she had been trying to prepare. 

 

“Nah, I’m not hungry.” You plopped on the couch, a groan escaping your lips as you felt another headache starting to form, similar to sensing a storm along the horizon. 

 

“You look like you need to go out, you’ve been in your room all week! It’s unlike you to keep to yourself, since I know you love being the center of attention.” She laughed, “I’m in the mood for some Karaoke, how about you?”

 

You froze, something had clicked inside your soul that had been closed until that moment. 

Karaoke.

A glinting tooth.

A wink from across the bar. 

Flirting, drinking, and whispers of promises of a night you wouldn’t forget.

 

Red and blue swirls danced across your vision as you recalled the best night of your life. The sudden recollection brought tears to your eyes. You could remember every touch, every word that had been exchanged. There were two things that had emerged in the night that you had never known before. 

One, your Soul had been summoned for the first time. The bright blue heart had emerged suddenly, and you had been startled, but he had calmed you down, explaining quickly that it was an accident. His had also been summoned, hidden away in his ribcage, the dimly lit heart becoming brighter as you held it. You had been amused as you watched the two hearts float and twirl above your entwined bodies, your nails raking along his spine, his shuddering groans encouraging your wandering hands. Your eyes had squeezed shut when you had reached your final climax of the night, and when you opened them, your souls were entwined as well, his shining a bright red when they separated, instead of the stark white it had been before. But as soon as they appeared, they had vanished. The rest was hazy, so you assumed you had fallen asleep soon after. 

Two, you had felt… Something. Something that brought a warmth to your mind, body, and soul when he touched you. Even recalling that night brought heat to your cheeks. You never blushed! You remembered the words that had dripped from his mouth, some sickly sweet, some downright filthy words, both holding the same kind of promise. A promise of something more. More than sex, more than pleasure. It was…

“Love.” You breathed out loud. That thought terrified you, yet you found yourself standing, grabbing your shoes. Jasmine yelled after you as you raced out the door. 

Against any sort of logic your mind could muster, you pushed forward. You were in a random t-shirt and athletic shorts (your pajamas) but you didn’t care. You probably looked like a mess as you marched down the sidewalk, determination behind every step you took, but that didn't matter. You took the feeling of being loved for the first time, the colors, the promises that had taken place the week before, and pushed it outwards into the air around you, radiating that energy. You weren’t aware of anything else besides trying to use your Soul to call out to him, sending a message through the whole damn neighborhood. The whole damn city. The whole damn world. He had made you feel like you were the only one on this world, and you were willing to embrace it. You felt like you were finally ready to let someone like that in your life. You focused in on your Soul, you could feel it pulsing in time with his, guiding every step you took.

At every crossroad, you could feel something similar to instinct beckoning you in one direction. It all felt like one path, that you couldn’t go another way if you tried. You had taken so many twists and turns that you were now well and deep into the downtown area of your city. You started walking faster, jogging, then running as you felt this tug on your heart becoming tighter and tighter, until it ceased all together, as you turned a corner. You saw his panting form, his back to you as he frantically looked around, sweat beading on his skull. His unzipped jacket flapped in the wind, giving him an intense, anime-like profile. Your heart swelled, and you knew that you had it bad. You suddenly knew that he had been searching for you, too. You stood there, frozen by the intense feelings that flowed through your mind and Soul, as you watched him slowly turn toward you, the world in slow motion. The people slowed, the breeze through the trees that lined the streets slowed. Everything was still as you locked eyes. You wanted to wave, to smile, to run toward him, but all you could muster was--

“Sans.”

His eyes widened, his pupils dilating as he finally seemed to come to his senses, and he started running. You didn’t want to waste any time as you both finally closed the space between, immediately pressing your lips to his teeth. You were worried you’d say something stupid, so you settled on no words altogether. The sickly heat you had felt earlier melted away into a comfortable warmth, the pain of your headache finally ceasing as you held each other for a moment. You were both breathing heavily, your breath taken away by the kiss, and the running frantically thorough the streets.

Sans groaned as the relief of finding you flowed through his body, holding onto that feeling for dear life. He had been just as sick as you, magical bodies becoming weaker while away from their soulmate. This thought had terrified him at first. The empty space beside him that morning had left a sickening feeling in his Soul, like he had lost something important. He had spent the first few days pacing, trying to figure out how he could see you again, but the connection between your Souls wasn’t strong enough for him to be able to track you in any way. The last few days he had sulked in his room, convinced that he had ruined his chances with his Soulmate, which he had never believed he could possess. How could a sinful skeleton possibly deserve the happiness that accompanies the concept of a Soulmate? In the Underground, Soulmates were holy property that no one else could possibly touch. It had been the one good thing that could happen to a weak and a strong Monster alike. The one thing that could make that miserable life somewhat decent. Connections that could never be broken were an important part of the tradition, but the presence of alcohol had halted this process for the two of you. The hole in your memory was keeping the bond that had been made from completing the connection. Instead of coalescing over time, it had formed in an instant, a rare event for Souls. 

“Stars, you finally remembered. Took ‘ya long enough. If I woulda known you would have gone and forgotten your ‘mate, I wouldn’t have gotten you that last shot,” He chuckled, holding your face in his hands, wiping away the tears you hadn’t realized had come to your eyes. 

You laughed, overwhelmed by it all, “I don’t even know what to do with myself right now, I have so many questions! How? Why are- Who- God, it’ll take me hours to ask you everything.” You buried your face in his jacket, hiding the stupid smile on your face, happiness filling up your entire being. 

A deep rumble vibrated from his chest, content to finally have you in his arms. You could feel the buzz of his Soul, pulsing to the beat of yours. He grabbed your chin and pulled it up to his face, kissing you deeply, before asking, “How’s about a lifetime?”

**Notes for the Chapter:**

> Perhaps I'll write an epilogue if any of you have questions on what comes next? 
> 
> Thanks so much for reading, and being patient! <3

**Author's Note:**

> BTW the songs I referenced are Believer by Imagine Dragons and Lydia by The Highly Suspect :3


End file.
